In certain situations, it is desirable that vehicles in motion have the ability to reliably exchange information. Various standards have been established for such vehicle-to-vehicle (V2V) communication via wireless networks. One common set of communication channels is known as dedicated short range communication (DSRC), implementing the IEEE 802.11p standard for wireless access in vehicle environments (WAVE). In the United States, 75 MHz of spectrum in the 5.9 GHz band (5.850-5.925 GHz) has been allocated for use in intelligent transportation systems. Other countries may allocate different portions of the RF spectrum for DSRC communications.
Inter-vehicle communication using DSRC may be especially useful when two or more large trucks (such as semis) wish to achieve certain efficiencies by platooning to reduce drag and save on fuel costs. Short to medium range communication in such a situation may be used to transmit control, status, situational, and/or audio and video data between the vehicles. Parallel communication on multiple channels between vehicles may be useful to provide all the data and information needed to maintain safe and effective platooning. However, this type of communication typically requires a direct line of sight between antennas of the two vehicles for the data to be transmitted properly.
Traditional antennas are insufficient for establishing reliable multi-channel short to medium range communication connections between moving trucks. Low gain or no gain antennas have been shown to be inappropriate for vehicle-to-vehicle communication because they often incur significant ground interference. However, off-the-shelf high-gain antennas appropriate for mounting on a vehicle provide communication over only a single channel and are rather bulky and unwieldy. For example, short and medium range communication antennas for 5.8-5.9 GHz bands, such as the ECOS product line by Mobile Mark, Inc., provide only a single channel. Therefore, in order to achieve multiple simultaneous channels of communication, multiple antennas may be needed at each installation location on each vehicle.
As will be explained in more detail below, the desirable installation location for antennas used for communication between large trucks is on or within the trucks' side-view mirrors. Consequently, establishing multiple channels of communication at each mirror can require four or more off-the-shelf antennas. Additionally, the ECOS antenna is rather bulky and expensive. When such off-the-shelf DSRC antennas are installed on the side mirror of a large truck (e.g. attached to the perimeter of the side mirror and protruding above the mirror), there is a high risk that the antenna will become detached from the mirror while the truck is in motion, for example when the truck is maneuvering through tight spaces or locations with a lot of vegetation.
It is therefore apparent that a need exists for a small, reliable antenna appropriate for multi-channel communication between large, moving vehicles.